Editing Analytical engine (section)

== Construction ==
Late in his life, Babbage sought ways to build a simplified version of the machine, and assembled a small part of it before his death in 1871.<ref name=":1" /><ref name="meccano" /><ref>{{cite book |title=Monthly Notices of the Royal Astronomical Society |date=1910 |publisher=Priestley and Weale |page=517 |url=https://books.google.com/books?id=hBjyAAAAMAAJ&q=%22A+few+years+before+his+death%22 |language=en}}</ref>

In 1878, a committee of the [[British Association for the Advancement of Science]] described the analytical engine as "a marvel of mechanical ingenuity", but recommended against constructing it. The committee acknowledged the usefulness and value of the machine, but could not estimate the cost of building it, and were unsure whether the machine would function correctly after being built.<ref>{{Cite report |title=Report of the Forty-Eighth Meeting of the British Association for the Advancement of Science |year=1879 |location=London |publisher=John Murray |url=https://www.biodiversitylibrary.org/item/94499#page/174/mode/1up |pages=92–102 |access-date=20 December 2015}}</ref><ref>{{cite web |url=https://www.fourmilab.ch/babbage/baas.html |title=The Analytical Engine (Report 1879) |publisher=Fourmilab.ch |access-date=20 December 2015}}</ref>

[[File:Analytical Engine (2290032530).jpg|thumb|[[Henry Babbage]]'s analytical engine mill, built in 1910,<ref name="mill" /> in the [[Science Museum (London)]]]]

Intermittently from 1880 to 1910,<ref>{{Cite book|url=https://books.google.com/books?id=osHuAAAAMAAJ&q=Munro+1910|title=Proceedings of the centenary assembly of the Institute of Actuaries|last=Britain)|first=Institute of Actuaries (Great|date=1950|publisher=Printed for the Institute of Actuaries at the University Press|pages=178|language=en}}</ref> Babbage's son [[Henry Prevost Babbage]] was constructing a part of the mill and the printing apparatus. In 1910, it was able to calculate a (faulty) list of multiples of [[pi]].<ref>{{Cite book|chapter-url=https://books.google.com/books?id=WtqpCAAAQBAJ|title=The Origins of Digital Computers: Selected Papers|last=Randell|first=Brian|date=21 December 2013|publisher=Springer|isbn=9783642618123|language=en|chapter=2.3. Babbage's Analytical Engine. H. P. Babbage (1910)}}</ref> This constituted only a small part of the whole engine; it was not programmable and had no storage. (Popular images of this section have sometimes been mislabelled, implying that it was the entire mill or even the entire engine.) Henry Babbage's "analytical engine mill" is on display at the Science Museum in London.<ref name="mill">{{cite web|url=https://collection.sciencemuseum.org.uk/objects/co62246/henry-babbages-analytical-engine-mill-1910-analytical-engine-mills |title=Henry Babbage's Analytical Engine Mill, 1910. |publisher=Science Museum |date=16 January 2007 |access-date=1 August 2012}}</ref> Henry also proposed building a demonstration version of the full engine, with a smaller storage capacity: "perhaps for a first machine ten (columns) would do, with fifteen wheels in each".<ref name="fourmilab">{{cite web |url=http://www.fourmilab.ch/babbage/hpb.html |title=The Analytical Engine (Henry P. Babbage 1888) |publisher=Fourmilab.ch |access-date=1 August 2012}}</ref> Such a version could manipulate 20&nbsp;numbers of 25&nbsp;digits each, and what it could be told to do with those numbers could still be impressive. "It is only a question of cards and time", wrote Henry Babbage in 1888, "... and there is no reason why (twenty thousand) cards should not be used if necessary, in an analytical engine for the purposes of the mathematician".<ref name="fourmilab" />

In 1991, the [[London Science Museum]] built a complete and working specimen of Babbage's [[Difference Engine No. 2]], a design that incorporated refinements Babbage discovered during the development of the analytical engine.<ref name="babbageonline" /> This machine was built using materials and [[engineering tolerance]]s that would have been available to Babbage, quelling the suggestion that Babbage's designs could not have been produced using the manufacturing technology of his time.<ref>{{cite web|url=https://www.computerhistory.org/babbage/modernsequel/ |title=A Modern Sequel&nbsp;— The Babbage Engine |publisher=Computer History Museum |access-date=1 August 2012}}</ref>

In October 2010, [[John Graham-Cumming]] started a "Plan 28" campaign to raise funds by "public subscription" to enable serious historical and academic study of Babbage's plans, with a view to then build and test a fully working virtual design which will then in turn enable construction of the physical analytical engine.<ref>{{cite news| url=https://www.bbc.co.uk/news/technology-11530905 | work=BBC News | title=Campaign builds to construct Babbage Analytical Engine | date=14 October 2010}}</ref><ref>{{cite web|url=http://plan28.org/ |title=Building Charles Babbage's Analytical Engine |publisher=Plan 28 |date=27 July 2009 |access-date=1 August 2012}}</ref><ref>{{Cite news|last=Markoff|first=John|date=7 November 2011|title=It Started Digital Wheels Turning|language=en-US|work=The New York Times|url=https://www.nytimes.com/2011/11/08/science/computer-experts-building-1830s-babbage-analytical-engine.html |archive-url=https://ghostarchive.org/archive/20220101/https://www.nytimes.com/2011/11/08/science/computer-experts-building-1830s-babbage-analytical-engine.html |archive-date=2022-01-01 |url-access=limited|access-date=2021-06-10|issn=0362-4331}}{{cbignore}}</ref> As of May 2016, actual construction had not been attempted, since no consistent understanding could yet be obtained from Babbage's original design drawings. In particular it was unclear whether it could handle the indexed variables which were required for Lovelace's Bernoulli program.<ref>{{cite web|title=Spring 2016 report to the Computer Conservation Society| publisher=Plan 28|url=http://blog.plan28.org/2016/05/spring-2016-report-to-computer.html| access-date=29 October 2016}}</ref> By 2017, the "Plan 28" effort reported that a searchable database of all catalogued material was available, and an initial review of Babbage's voluminous Scribbling Books had been completed.<ref>{{Cite web|url=http://blog.plan28.org/2017/05/spring-2017-report-to-computer.html|title=Spring 2017 report to the Computer Conservation Society|website=blog.plan28.org|access-date=13 June 2017}}</ref>

Many of Babbage's original drawings have been digitised and are publicly available online.<ref>{{Cite web|date=1821–1905|title=The Babbage Papers|url=https://collection.sciencemuseumgroup.org.uk/documents/aa110000003/the-babbage-papers|url-status=live|website=Science Museum Group|archive-url=https://web.archive.org/web/20200413021056/https://collection.sciencemuseumgroup.org.uk/documents/aa110000003/the-babbage-papers |archive-date=13 April 2020 }}</ref>